Your company registers the domain name of contoso.com. You plan to deploy two web servers, two application servers, and two Microsoft SQL server instances on Microsoft Azure virtual machines. All of t

Configuring the Azure virtual network to use custom DNS servers ensures that all virtual machines in the VNet can resolve FQDNs from the custom domain, allowing access to the Availability Group listener.

Adding a subnet to the Azure virtual network is for network segmentation and does not directly contribute to FQDN resolution for an Availability Group listener.

Deploying a domain controller and joining virtual machines to the domain is essential for creating an Active Directory-integrated DNS server that can host the custom domain and register the AlwaysOn Availability Group listener's FQDN.

Registering a DNS server on the Azure virtual network typically refers to configuring the VNet's DNS settings, which is encompassed by action A in this context for enabling resolution.

Using the Azure provided name resolution service is insufficient as it cannot resolve custom domain FQDNs for internal resources like an AlwaysOn Availability Group listener.

Deploying a DNS server provides the necessary infrastructure to host custom DNS zones, like contoso.com, and allows for the resolution of internal FQDNs for services such as the SQL AlwaysOn Availability Group listener.